I am so sorry to hear about your dad. But - it is not necessarily the death sentence it once was. many folks on this forum have fought cancer and won, for now. Some have not and are no longer with us.
my dad - my best friend, mentor, sailing and drinking buddy, to it 18 months ago.
Alas I cannot take your charter
- but I can suggest something. Do the charter
with your family
and your dad anyway!!! if he was only just diagnosed, he's almost certainly got time to do it, and it may be something you look back on in the future as a wonderful and very important occasion.
Seriously - do it anyway. you won't regret it.
best of luck-